1. Field of the Invention
Exemplary embodiments of the present invention relate to an optical sensor and a manufacturing method of an optical sensor. More particularly, exemplary embodiments of the present invention relate to an optical sensor that prevents damage to a semiconductor layer, that prevents a short circuit, and that prevents a disconnection of a source electrode and a drain electrode, and a manufacturing method of the optical sensor.
2. Discussion of the Background
A liquid crystal display (LCD), as a flat panel display that is most widely used at present, is a display device that is constituted by two substrates with electrodes and a liquid crystal layer interposed therebetween to control the amount of light transmitted by rearranging liquid crystal molecules of a liquid crystal layer by applying a signal to the electrodes.
Recently, research on liquid crystal displays having a touch sensing function or an image sensing function has been undertaken. To realize the touch sensing function and the image sensing function, a light sensor including an infrared ray sensing thin film transistor, a visible sensing thin film transistor, and a switching thin film transistor may be added to the liquid crystal display.
The infrared ray sensing thin film transistor has different characteristics from the visible ray sensing thin film transistor and the switching thin film transistor, and therefor the semiconductor layer of the infrared ray sensing thin film transistor is formed of different materials than the semiconductor layers of the visible ray sensing thin film transistor and the switching thin film transistor. Accordingly, one dry etch process is required to form the semiconductor layer of the infrared ray sensing thin film transistor and one dry etch process is required to form the semiconductor layers of the visible ray sensing thin film transistor and the switching thin film transistor. That is, two dry etch processes are executed to form the semiconductor layers.
Here, if the semiconductor layers of the visible ray sensing thin film transistor and the switching thin film transistor is firstly formed, the semiconductor layers of the visible ray sensing thin film transistor and the switching thin film transistor may be damaged in the process of forming the semiconductor layer of the infrared ray sensing thin film transistor as a following process.
In contrast, if the semiconductor layer of the infrared ray sensing thin film transistor is firstly formed, the semiconductor layer of the infrared ray sensing thin film transistor may be damaged in the process of forming the semiconductor layers of the visible ray sensing thin film transistor and the switching thin film transistor as the following process.
When forming the semiconductor layer as the following process, an insulating layer may be formed under the semiconductor layer, however, as shown in FIG. 1 and FIG. 2, this insulating layer remains on the semiconductor layer that is firstly formed such that a step due thereto is large, and thereby a short circuit or a disconnection of the overlying source electrode and drain electrode may be generated.
Also, an etch stopper may be formed on the semiconductor layer that is firstly formed, however, as shown in FIG. 3 and FIG. 4, the etch stopper may be corroded by a chlorine-based gas (including Cl2) used when etching the semiconductor layer. Accordingly, as shown in FIG. 5, the semiconductor layer positioned under the etch stopper may be deteriorated, and the short circuit and the disconnection of the overlying source electrode and drain electrode may be generated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form any portion of the prior art nor what the prior art may suggest to a person of ordinary skill in the art.